Devices for towing vehicles are well known in the art and generally consist of a wheel lift system attached to a towing vehicle. The wheel lift system is adapted to support the wheels of a vehicle to be towed. One end of the towed vehicle is then elevated by a hydraulic mechanism, with the longitudinal axis of the towed vehicle forming an obtuse angle with respect to the ground. Vehicle towing devices may be organized into two categories, commercial and consumer. Commercial vehicle towing devices are commonly associated with tow trucks and are mounted so that the towing devices extend from the towing vehicle on a continuous basis. This facilitates quick and easy access to the towing devices which makes the business of towing more profitable by reducing the time necessary to attach and detach vehicles to the towing device.
Consumer vehicle towing devices are, on the other hand, not typically designed to extend from the towing vehicle on a continuous basis. This results from both the periodic nature of the use of consumer vehicle towing devices, as well as the desire to avoid the driving difficulty presented by having the same extending from the towing vehicle. Further, vehicle towing devices often detract from the aesthetics of the towing vehicle. Thus, most consumer towing devices are designed to be removably mounted to the towing vehicle so that they may be easily removed. An example of a prior art consumer towing device is a removable two-ball.
U.S. Pat. No. 4,993,911 to Grant discloses a commercial towing device that comprises of a mobile crane for a towing truck. The crane includes, inter alia, a boom that is operably connected to hydraulic rams to vary the boom's longitudinal and angular positions. The boom is pivotally mounted to a mast structure. Both the hydraulic rams and the mast structure are braced against a pivot structure that is secured to the bed of the truck. In this fashion, horizontal components of forces produced during lifting and towing of a load, and imposed by the hydraulic rams, is offset by the opposing horizontal components of forces imposed upon the braces by the load.
U.S. Pat. No. 5,064,078 to Van Staveren discloses another commercial towing device that is a combination portable hoist, crane and vehicle towing apparatus. As a portable hoist, a vertical mast and hydraulically actuated boom are mounted on a standard support having support legs oriented in a "V", with the hoist boom positioned between the support legs. As a portable crane, the mast and boom are mounted onto a platform attached to a truck bumper to allow 360.degree. rotation about an axis of the vertical mast. In this configuration, the portable crane can load and remove objects to/from a bed of a truck. As an automobile towing mechanism, the mast and boom are locked in position within the plane of movement of the boom normal to the vehicle bumper. A typical automobile bumper and axle attachment towing device is attached to the boom chain. Stabilizer bars orient the bumper and axle attachment towing device parallel to and spaced-apart from the vehicle bumper. This allows the tow vehicle to elevate one end of a towed vehicle.
U.S. Pat. No. 5,123,802 to Bell discloses still another commercial towing device for a motorcycle which includes a wheel lift adapter kit having, inter alia, a plurality of rigid bars which form a pair of spaced cradles, each of which is attached to a cross bar assembly. The cross bar assembly is attached to one end of a retractable boom. The opposite end of the boom is attached to the rear of a towing vehicle. The boom is telescoping and may be pneumatically or hydraulically extended or retracted. The boom is pivotally mounted to the rear of the vehicle so that it may be lowered to the ground or raised therefrom, elevating a motorcycle.
U.S. Pat. No. 5,326,216 to Russ discloses a commercial vehicle towing device for trucks which includes, inter alia, a frame having a pair of spaced-apart channels terminating in a tail positioned at the rear of the truck. A base is movably mounted within the channels. The base includes a subtending pivoting arm. The arm extends from the base, terminating in a telescoping housing. The housing is positioned to extend from the rear of the truck to which it is attached and terminates in a support member that extends transverse to the telescoping housing. Each end of the support member terminates in a wheel mount adapted to selectively engage the wheels of a vehicle to be towed. A first hydraulic mechanism is connected between the tail mount and the base to move the base along the channels. A second hydraulic mechanism is connected between the tail mount and the telescoping housing to lower and raise the housing closer to and farther from the ground. A third hydraulic mechanism is connected between the wheel mounts to vary the distance therebetween.
A major concern with a towing device concerns avoiding damage to the towed vehicle, the towing vehicle and the towing device when crossing over uneven terrain, e.g., a dip in the ground, a ramp or a drive-way. When the rear end of the towing vehicle, and front end of towed vehicle traverse opposing sides of a recess in the ground, the rigidity of the towing device may cause the rear wheels of the towing vehicle to be lifted off the ground, referred to as "high centering". This may subject the towing device to undue strain, resulting in catastrophic failure of the same.
It is an object, therefore, of the present invention to provide a towing device that facilitates traversing uneven terrain by avoiding high centering of a towing vehicle.
It is a further object of the present invention to provide a lightweight towing device that is easily stored underneath the towing vehicle.